From 680ac11ef97e2ed04b2f6b5e387086466ae81676 Mon Sep 17 00:00:00 2001
From: Vasiliy Tolstov <v.tolstov@unistack.org>
Date: Sun, 27 Mar 2022 00:16:22 +0300
Subject: [PATCH] client: determenistic retry backoff

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>
---
 client/backoff.go      | 17 ++++++++++++++++-
 client/backoff_test.go |  2 +-
 client/client.go       |  4 ++--
 client/retry.go        | 20 +++++++++++++++++---
 4 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/client/backoff.go b/client/backoff.go
index 0aed7c60..d548b724 100644
--- a/client/backoff.go
+++ b/client/backoff.go
@@ -2,6 +2,7 @@ package client
 
 import (
 	"context"
+	"math"
 	"time"
 
 	"go.unistack.org/micro/v3/util/backoff"
@@ -10,6 +11,20 @@ import (
 // BackoffFunc is the backoff call func
 type BackoffFunc func(ctx context.Context, req Request, attempts int) (time.Duration, error)
 
-func exponentialBackoff(ctx context.Context, req Request, attempts int) (time.Duration, error) {
+// BackoffExp using exponential backoff func
+func BackoffExp(_ context.Context, _ Request, attempts int) (time.Duration, error) {
 	return backoff.Do(attempts), nil
 }
+
+// BackoffInterval specifies randomization interval for backoff func
+func BackoffInterval(min time.Duration, max time.Duration) BackoffFunc {
+	return func(_ context.Context, _ Request, attempts int) (time.Duration, error) {
+		td := time.Duration(time.Duration(math.Pow(float64(attempts), math.E)) * time.Millisecond * 100)
+		if td < min {
+			return min, nil
+		} else if td > max {
+			return max, nil
+		}
+		return td, nil
+	}
+}
diff --git a/client/backoff_test.go b/client/backoff_test.go
index 5b9b60b8..2ab854f7 100644
--- a/client/backoff_test.go
+++ b/client/backoff_test.go
@@ -22,7 +22,7 @@ func TestBackoff(t *testing.T) {
 	}
 
 	for i := 0; i < 5; i++ {
-		d, err := exponentialBackoff(context.TODO(), r, i)
+		d, err := BackoffExp(context.TODO(), r, i)
 		if err != nil {
 			t.Fatal(err)
 		}
diff --git a/client/client.go b/client/client.go
index 63cb4f85..71bedfd9 100644
--- a/client/client.go
+++ b/client/client.go
@@ -14,8 +14,8 @@ var (
 	DefaultClient Client = NewClient()
 	// DefaultContentType is the default content-type if not specified
 	DefaultContentType = "application/json"
-	// DefaultBackoff is the default backoff function for retries
-	DefaultBackoff = exponentialBackoff
+	// DefaultBackoff is the default backoff function for retries (minimum 10 millisecond and maximum 5 second)
+	DefaultBackoff = BackoffInterval(10*time.Millisecond, 5*time.Second)
 	// DefaultRetry is the default check-for-retry function for retries
 	DefaultRetry = RetryNever
 	// DefaultRetries is the default number of times a request is tried
diff --git a/client/retry.go b/client/retry.go
index 40272fd2..a218b3fe 100644
--- a/client/retry.go
+++ b/client/retry.go
@@ -19,18 +19,32 @@ func RetryNever(ctx context.Context, req Request, retryCount int, err error) (bo
 	return false, nil
 }
 
-// RetryOnError retries a request on a 500 or timeout error
+// RetryOnError retries a request on a 500 or 408 (timeout) error
 func RetryOnError(_ context.Context, _ Request, _ int, err error) (bool, error) {
 	if err == nil {
 		return false, nil
 	}
-
 	me := errors.FromError(err)
 	switch me.Code {
 	// retry on timeout or internal server error
 	case 408, 500:
 		return true, nil
 	}
-
 	return false, nil
 }
+
+// RetryOnErrors retries a request on specified error codes
+func RetryOnErrors(codes ...int32) RetryFunc {
+	return func(_ context.Context, _ Request, _ int, err error) (bool, error) {
+		if err == nil {
+			return false, nil
+		}
+		me := errors.FromError(err)
+		for _, code := range codes {
+			if me.Code == code {
+				return true, nil
+			}
+		}
+		return false, nil
+	}
+}